1. Field of the Invention
The present invention relates to fluid systems. The invention concerns, more particularly, a method for joining two components of a fluid system. The fluid system utilizes polymer components and finds particular use in footwear sole structures.
2. Description of Background Art
The primary elements of conventional footwear are an upper and a sole structure. Athletic footwear sole structures are generally formed of three layers, customarily referred to as an insole, a midsole, and an outsole. The insole is a thin, cushioning member located adjacent to the foot that improves footwear comfort. The midsole, typically formed of polyurethane or ethylvinylacetate foam, imparts both ground reaction force attenuation and energy absorption. The outsole provides a wear-resistant, ground-contacting surface.
Midsoles often incorporate fluid-filled bladders to enhance the ground reaction force attenuation and energy absorption characteristics of the sole structure. Fluid-filled bladders may be manufactured through a flat sheet bonding technique, as disclosed in U.S. Pat. Nos. 4,183,156 and 4,219,945, both to Rudy, in which two separate sheets of elastomeric film are formed having the overall peripheral shape of the bladder. The sheets are then bonded together along the periphery to form a bladder having upper, lower, and side surfaces, and at predetermined interior areas to give the bladder a desired configuration. Another method of manufacturing fluid-filled bladders is a blow-molding process, as generally disclosed in U.S. Pat. No. 5,353,459 to Potter et al., wherein a liquefied elastomeric material is placed in a mold having the desired overall shape and configuration of the bladder. The mold has an opening at one location through which pressurized air is provided. The pressurized air forces the liquefied elastomeric material against the inner surfaces of the mold and causes the material to harden in the mold, thereby forming a bladder with the desired shape and configuration. In addition, fluid-filled bladders may be manufactured through a vacuum-forming process, as disclosed in U.S. Pat. No. 5,976,451 to Skaja, et al., wherein a pair of sheets of flexible thermoplastic resin in which the sheets are placed against a pair of molds having a vacuum system for properly shaping the two sheets. The mold portions are then closed to seal the two sheets around their peripheries and form the bladder.
Sole structures may also incorporate fluid systems that include various components, including a pressure chamber, a pump chamber for increasing the pressure in the pressure chamber, one or more valves for regulating the direction and rate of fluid flow, and conduits that connect the various fluid system components. Fluid systems of this type, which are sealed to prevent the entry or exit of ambient air, are disclosed in U.S. Pat. No. 5,950,332 to Lain, U.S. Pat. No. 5,794,361 to Sadler, and U.S. Pat. No. 4,446,634 to Johnson et al., all hereby incorporated by reference. Similar systems, which utilize ambient air as the system fluid, are disclosed in U.S. Pat. No. 6,085,444 to Cho, U.S. Pat. No. 5,937,462 to Huang, and U.S. Pat. No. 5,558,395 to Huang, all hereby incorporated by reference.
Fluid systems may require multiple valves and chambers that are interconnected by various conduits. Simple fluid systems may be manufactured such that the various components are formed integral with each other. More complex fluid systems, however, require that the individual components be formed separately and subsequently incorporated into the fluid system. Accordingly, the components must be joined together in a manner that prevents the fluid contained by the system from escaping through the joint, but also places the joined components in fluid communication. In addition, the individual components may be formed from different materials; may be formed from flexible materials; and may be formed through different manufacturing processes, such as flat sheet bonding, vacuum forming, and blow molding. The present invention is a method for joining fluid system components of this type.